In view of the properties of fluorine, such as low refractive index and transparency, fluorine-containing compounds are useful in the field of resist technologies. Among others, hexafluorohydroxyisopropyl unit-containing compounds not only show high transparency at each wavelength because of their high fluorine content but also work effectively for improvement of hydrophilicity and adhesion due to the coexistence of a polar hydroxyl group in their compound structure (see Patent Document 1).
Norbornanyl esters of the general formula [3], which are the target compound of the present invention, are α-substituted acrylic esters each having a norbornanyl group with a hexafluorohydroxyisopropyl unit-containing carbon chain and are useful as resist monomers.
In general, the α-substituted acrylic esters can be synthesized by the following ester synthesis processes: (A) reaction of a carboxylic halide and an alcohol; (B) reaction of a carboxylic acid anhydride and an alcohol; (C) dehydration condensation reaction of a carboxylic acid and an alcohol; and (D) transesterification reaction of a carboxylic acid ester and an alcohol.
For example, Non-Patent Document 1 discloses a process of synthesizing cyclohexyl acrylate by transesterification reaction of methyl acrylate and cyclohexanol. Patent Document 1 discloses a process of synthesizing a norbornanyl ester by reaction of a norbornanyl alcohol and an α-substituted acrylic chloride.
Each of these processes is characterized in that the alcohol is used as the reaction substrate. In order to apply these processes for synthesis of the target compound of the present invention, it is necessary to first convert a norbornene of the general formula [1] to a norbornanyl alcohol of the general formula [4] by a hydroboration technique, an ester addition-ester hydrolysis technique etc., and then, react the norbornanyl alcohol with an acrylic acid, acrylic halide, acrylic anhydride or acrylic ester of the general formula [2′] as indicated in Scheme 1. Moreover, the norbornanyl alcohol intermediate (the general formula [4]) has a high viscosity and thus raises a problem in process operation. (The definitions of R1 to R5 in the general formula [3] of Scheme 1 will be described later; and the definitions of R1 to R5 in the general formulas [1], [2′] and [4] are the same as those in the general formula [3].)

In contrast to these processes, Patent Document 2 and Patent Document 3 each disclose a process of reacting a norbornene with (meth)acrylic acid in the presence of an acid catalyst.
Further, Patent Document 4 discloses a process of reacting a substituted norbornene with an α-substituted acrylic acid in the presence of a specific acid catalyst so as to allow addition of the acid to an olefin moiety of the norbornene and thereby form a corresponding ester compound. It is also reported that p-toluenesulfonic acid, trifluoroacetic acid and trifluoromethanesulfonic acid are particularly suitable as the acid catalyst.
In Patent Document 4, the target norbornanyl ester can be obtained with less number of process steps and without going through the high-viscosity norbornanyl alcohol intermediate. The process of Patent Document 4 can be thus regarded industrially superior to the processes that proceed through the norbornanyl alcohol intermediate even though there occurs formation of by-products in this process.